1. Field of the Invention
The present invention relates to a uni-morph, bi-morph or other types of piezoelectric or electrostrictive elements which undergo displacement in the form of bending, deflection or flexture and which can be used for ink jet print heads, microphones, sounding bodies (such as loudspeakers), various resonators or vibrators, sensors, and other components or devices. The term "element" used herein is an element capable of transducing or converting an electric energy into a mechanical energy, i.e., mechanical force, displacement, strain or vibrations, or transducing such a mechanical energy into an electric energy. Further, the element of the invention has a dielectric property in addition to a piezoelectric/electrostrictive property, and therefore can be used as a film-like capacitor element.
2. Discussion of the Prior Art
In the recent years, in the fields of optics and precision positioning or machining operations, for example, there have been widely used and increasingly demanded an element whose displacement can be controlled for adjusting or controlling an optical path length or the position of a member or component of a device, on the order of fractions of a micron (.mu.m), and a detecting element adapted to detect infinitesimal displacement of a subject as an electric change. To meet this need, there have been developed various piezoelectric or electrostrictive actuators or sensors utilizing a piezoelectric or electrostrictive material such as a ferroelectric material, which exhibits the reverse or converse piezoelectric effect or the electrostrictive effect, in which such a piezoelectric or electrostrictive material produces a mechanical displacement upon application of a voltage or electric field thereto, or which exhibits the piezoelectric effect in which the piezoelectric material produces a voltage or electric field upon application of pressure or mechanical stress.
For example, an ink jet print head uses a piezoelectric/electrostrictive element of a conventional uni-morph or bi-morph type, which is required to permit a high-quality high-speed printing operation. To this end, developments have been made to reduce the size and required drive voltage of the piezoelectric/electrostrictive element, and improve the operating response of the element.
A piezoelectric or electrostrictive element of the above type is carried by a substrate, which functions as an oscillator or transducer plate. For assuring sufficient amount and force of bending or flexural displacement of the substrate or plate, it is important to reduce the thickness of the substrate, on the one hand. On the other hand, however, the reduction in the substrate thickness undesirably results in a decrease in the mechanical strength of the substrate. In addition, the piezoelectric or electrostrictive element of the conventional uni-morph or bi-morph type is unsatisfactory in its operating reliability since planar members such as piezoelectric/electrostrictive plates which constitute the element are bonded to each other by means of adhesives, for example.